During construction, constant measurements must be taken to insure that the structure is adhering to the design being built. Many times a scanner and/or total stations are used to take these measurements. A total station is an electronic/optical instrument used in modern surveying. The total station is an electronic theodolite (transit) integrated with an electronic distance meter (EDM) to read distances from the instrument to a particular point.
The total station, and most all other devices, need to be stable in order to make precise measurements. However, in many situations, the surface near where the device must be set does not allow a tripod to provide a stable surface. Other times it is just inconvenient or very difficult to use a tripod due to the state of the surface. In some cases, metal or wood decking is set as a form before the concrete floors are poured which is not a stable footing for a tripod.